Apnea refers to suspension of external breathing. During apnea there is little or no movement of the muscles of respiration and the volume of the lungs essentially remains unchanged. Severe tissue damage, brain damage and death can result. Oxygenation during apnea is called apneic oxygenation. Continuous apneic oxygenation delivered to the lower end of the trachea has been found to maintain trauma patients for up to one hour following injury. Despite these findings, there has yet to be an apneic oxygenation catheter developed for use in the field by emergency medical technicians (EMTs) or the military.
A cricothyrotomy is an incision through the cricothyroid membrane above the cricoid cartilage readily evident just above the trachea, and is considered less invasive than an incision through the trachea (tracheotomy) and to have fewer complications. Cricothyrotomy ventilation is often necessary to secure the airway in injuries requiring apneic oxygenation. When there is an obstruction in the airway and endotracheal intubation is not possible, an immediate solution is to insert a tube through a hole in the cricothyroid membrane. In some cases the bypass will allow the patient to breathe on their own. In other instances the bypass will provide an entry way for assisted ventilation and/or drug delivery.
Generally, the devices available to perform emergency cricothyrotomies require a skilled practitioner and require many steps to secure the airway. One example device and procedure are described in U.S. Pat. No. 4,677,978. There, a derivative of the Seldinger method is used making the installation of this device labor intensive. First, a scalpel is used to make an incision into the cricothyroid membrane. Next, an over-the-needle catheter is entered into the airway with a syringe. The syringe and needle are then removed, leaving the catheter in place. Following that, a guide wire is inserted into the catheter, and the catheter is removed. Finally a dilator is inserted over the guide wire and the guide wire is removed.
Other devices such as those described in U.S. Pat. No. 4,869,718 do not use the Seldinger method and therefore require fewer steps. However, these devices only provide a small opening for the catheter and are limited to high frequency jet ventilation.